This invention relates generally to an electrical connector and, more particularly, to a zero insertion force electrical connector having cam means therein for actuating the contacts out of engagement with conductors on an electrical component.
It is well known in the art that substantial force is required to insert a printed circuit board into a connector having a large number of spring contacts therein due to the resilient engaging force of the contacts with the edge of the board. As the number of contacts is increased in a connector, the amount of force required to insert the printed circuit board into the connector, or to withdraw it from the connector, may become excessive for practical use. In addition, direct insertion of boards into connectors having spring contacts therein results in a wiping action occurring between the contacts and the conductive traces on the edge of the board, which may cause excessive wear of the traces over lengthy periods of use of the connector. It is, therefore, a common practice in the art to provide a zero insertion force printed circuit board connector in which the contacts are mounted out of the path of movement of the board when it is inserted into the connector whereby no resistance is encountered upon inserting the board thereinto.
There are two general types of zero insertion force connectors, one in which the contacts are normally closed and the other in which the contacts are normally open. In the case of a connector having normally open contacts, the contacts are normally unloaded (that is, no stresses are applied to the contacts) and the contacts are cammed against the printed circuit board. In a connector having normally closed contacts, the contacts are preloaded in the connector housing in a position to resiliently engage a printed circuit board mounted therein and a cam actuator is provided for retracting the contacts away from the standard engagement position so that a board may be inserted into the housing with zero insertion force. The present invention relates to a zero insertion force connector having normally closed contacts.
U.S. Pat. Nos. 3,899,234 and 3,963,317 disclose normally closed contact-type zero insertion force printed circuit board connectors in which the cam actuating mechanism for retracting the two rows of contacts in each connector is disposed between the two rows. This arrangement has the disadvantage that it necessarily requires that the two rows of contacts be spaced apart a greater distance than would otherwise be required if the actuator were not employed.
U.S. Pat. Nos. 3,537,063 and 3,818,419 also disclose normally closed contact-type zero insertion force printed circuit board connectors, but in these connectors the cam actuators are not disposed between the two rows of contacts therein thus permitting a closer spacing between the two rows of contacts in the connectors. However, the cam actuating mechanism in U.S. Pat. No. 3,537,063 comprises two rotatable cam shafts which act independently and are subject to high torsional forces which does not permit uniform actuation of the contacts. The connector disclosed in U.S. Pat. No. 3,818,419 has the disadvantage that the cam actuating mechanism moves laterally thereby necessitating a relatively wide connector housing. Another prior connector of interest is disclosed in U.S. Pat. No. 4,050,758, assigned to the assignee of the present application.
It is therefore one object of the present invention to provide an improved normally closed contact-type zero insertion force printed circuit board connector in which the cam actuating means is disposed outside the two rows of contacts in the connector housing to allow close spacing of the rows of contacts, and also which is relatively simple, compact, and provides uniform actuation of the contacts.
Normally closed zero insertion force printed circuit board connectors have very little wiping action between the contacts and the boards mounted therein when mated and actuated and, therefore, reliable electrical contact is not always achieved. Any contact wiping which results in normally caused by contact surface irregularities which is random in nature or by unintentional shifts in the housing/contact relationships due to unbalanced stresses. It is therefore another object of the present invention to provide a zero insertion force printed circuit board connector which will effect sufficient wiping action between the contacts and the traces on the printed circuit board to provide reliable electrical contact therebetween.